Do i need to worry about baffel step correction if i measure all my drivers in the finished speaker cabinet or will that measurement already account for it? Thanks! Travis
Nearfield measurement does not account for it. That would need a baffle step simulation and correction.
Fafield measurement will account for baffle influence, ideally you measure at the actual listening distance - but that also has some disadvantages.
Vituixcad can correct (by simulating baffle) measurements of any measuring distance.
I'd say no worry, since your speakers are in the real situation they will be used.
That doesn't mean that - in accordance with what you measure vs. what you have designed, or calculated- you may not need or check some crossover corrections. But normally, this should be directly taken in count by your measurement, since you measure the real thing.
Edit : yes, except in near field measurement, as justifiably mentioned by @stv ! But if you measure at enough distance, outside, like I often do (below), you should have a correct speaker integration so no problem...
T
I havent measured any speakers myself yet, is nearfield like 50 to 100 cm away, or is near field right next to the dustcap?
5mm from the dust cap. Just inside the port if measuring a port
For me, far-field means the acoustic far-field, where phase between drivers is no longer chaotic and speaker behaves at inverse square law, SPL vs distance.
Rule of thumb for that distance is typically about 3X longest speaker dimension, so speaker specific.
(Any measurements inside this distance are usually pretty suspect.)
So I just try to quote measuring distances as they were made.....dust cap, 1m, ...whatever actually distance.
The far field distance varies with frequency.
SynAudCom
https://www.prosoundtraining.com/2010/06/28/far-field-criteria-for-loudspeaker-balloon-data/
In regard to full range frequency measurements, Pat Brown wrote :
"A working “rule-of-thumb” for determining the boundary between near-field and far-field is to make the minimum measurement distance the longest dimension of the loudspeaker multiplied by 3.
While this estimate is generally acceptable for field work, it ignores the frequency-dependency of the transition between the near and far fields."
He then writes:
"It is often thought that a remote measurement position is necessary for low frequencies since their wavelengths are long. Actually the opposite is true. It is more difficult to get into the far-field of a device at high frequencies, since the shorter wavelengths make the criteria in Item 4 more difficult to satisfy.
Item 4:
4. The distance from the source where the path length difference for wave arrivals from points on the device on the surface plane perpendicular to the point of observation are within one-quarter wavelength at the highest frequency of interest (Figure 2)."
"Fig. 2- The figure show the path length difference to the microphone position for a loudspeaker whose largest dimension is 2 feet. Note that even though the transducer is smaller than the cabinet face, the entire front baffle of the enclosure can radiate energy. Attenuation balloons for this loudspeaker can be measured up to 17kHz at 9 meters. The upper practical limit for loudspeaker modeling is 10kHz."
An important distinction between high frequency and low frequency measurement, criteria #4 can be satisfied up to 210Hz for a subwoofer with a one square meter face measured at one meter with a measurement mic on the ground plane.
If you measure like you often do with the microphone well above the ground plane, you also need to account for the ground reflection cancellation due to the path length difference between the direct and reflected sound.
That dip varies in frequency with mic distance from the speaker and it's height above the ground.
Art
Yes indeed. It was included in the measuring software I used. Moreover, I often did those outside measurements at night, when the air is calm and silent... 😉
That's it, exactly.
T
If you mean do you have to fix it using separate components, no you don't. You can make the response right in all respects in one go if that's possible.
To be clear, the word nearfield has no meaning unless it's specified what it is near to.
Thanks for the knowledge guys! Im building a 3way center channel so ill have some more questions soon! -Travis
The centers that I've built needed virtually no BSC. Tonal balance for vocals was much better without.
My music speakers, or mains are built with close to full BSC. They are further away from the walls, and floor.
I wanted a 10" 3-way for a center in a short tower that sits on the floor. Due to the woofer being close to the floor, I could only get the tonal balance I wanted by using EQ. My mid was not high enough sensitivity to get a more forward voicing. The EQ in my AVRs, is rather basic, and I can't really get the EQ needed to be completely satisfied. I move equipment between two rooms, and keeping track of EQ settings for various centers was a PITA. What worked for me was a 6.5" 2-way.
My music speakers, or mains are built with close to full BSC. They are further away from the walls, and floor.
I wanted a 10" 3-way for a center in a short tower that sits on the floor. Due to the woofer being close to the floor, I could only get the tonal balance I wanted by using EQ. My mid was not high enough sensitivity to get a more forward voicing. The EQ in my AVRs, is rather basic, and I can't really get the EQ needed to be completely satisfied. I move equipment between two rooms, and keeping track of EQ settings for various centers was a PITA. What worked for me was a 6.5" 2-way.
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